1. Field of the Invention
The invention relates to a connecting and disconnecting apparatus of a clutch or a brake or the like. More particularly, the invention relates to a dual connecting and disconnecting apparatus in which a pair of connecting and disconnecting apparatuses are arranged in series in the axial direction.
2. Description of the Related Art
A vehicular automatic transmission is known which uses a plurality of planetary gearsets, clutches, and brakes. The automatic transmission disclosed in Japanese Patent Laid-Open Publication No. 2001-304355, which is one such example, is provided with a dual connecting and disconnecting apparatus having (i) a first hydraulic cylinder in which a piston is moved in a first direction which is parallel with an axis of the dual connecting and disconnecting apparatus by supplying hydraulic fluid into a pressure chamber, (ii) a second hydraulic cylinder which is integrally provided on a common support member (i.e., an input shaft 2) and which is concentric with the first hydraulic cylinder in a position adjacent in the first direction to the first hydraulic cylinder, and in which a piston is moved in the first direction by supplying hydraulic fluid into a pressure chamber, (iii) a cylindrical connecting drum provided on a side wall portion of a cylinder tube of the first hydraulic cylinder integrally mounted to the support member, the connecting drum being centered around the axis and protruding out in the first direction; (iv) a first friction engaging device (i.e., a clutch) positioned farther to the first direction side than the second hydraulic cylinder, the first friction engaging device having (a) a plurality of friction members provided on the connecting drum, this connecting drum being rotatable around the axis with respect to a first connecting member (i.e., a sun gear), the plurality of friction members being non-rotatable with respect to the connecting drum, and (b) a plurality of friction members provided on the first connecting member, the plurality of friction members being non-rotatable with respect to the first connecting member, the first friction engaging device connecting the support member with the first connecting member via the connecting drum by moving the piston of the first hydraulic cylinder in the first direction and engaging the plurality of friction members of the connecting drum with the plurality of friction members of the first connecting member; and (v) a second friction engaging device (i.e., a clutch) positioned farther to the first direction side than the second hydraulic cylinder and adjacent in the axial direction to the first friction engaging device, the second friction engaging device having (a) a plurality of friction members provided on the connecting drum, this connecting drum being rotatable around the axis with respect to a second connecting member (i.e., a sun gear), the plurality of friction members being non-rotatable with respect to the connecting drum, and (b) a plurality of friction members provided on the second connecting member, the plurality of friction members being non-rotatable with respect to the second connecting member, the second friction engaging device connecting the support member with the second connecting member via the connecting drum by moving the piston of the second hydraulic cylinder in the first direction and engaging the plurality of friction members of the connecting drum with the plurality of friction members of the second connecting member. The piston of the first hydraulic cylinder also serves as a cylinder tube of the second hydraulic cylinder. That piston is engaged with the connecting drum so as to be non-rotatable with respect thereto. The friction members of the second friction engaging device are fitted to the piston so as to be non-rotatable with respect thereto and held in position by a stopper member (i.e., a snap ring) attached to the piston.
In this kind of dual connecting and disconnecting apparatus, however, because the second hydraulic cylinder and the second friction engaging device within the cylinder type of the first cylinder are able to move in the axial diction, the sliding resistance and the like of these parts results in the hydraulic pressure in one of the pressure chambers affecting the hydraulic pressure in the other pressure chamber. As a result, it is difficult to finely control both the engaging torque of the first friction engaging device and the engaging torque of the second friction engaging device at the same time, thereby restricting the use of the two friction engaging devices.
Furthermore, because the friction members of the second friction engaging device are fitted to the piston of the first hydraulic cylinder so as to be non-rotatable with respect thereto, a cylindrical drum and spline teeth or the like must be provided on the piston in addition to the connecting drum provided on the cylinder tube, which results in a complex piston shape and high manufacturing costs. Also, because torque is transmitted via the piston of the first hydraulic cylinder when the second friction engaging device is engaged, the operating resistance of the piston of the first hydraulic cylinder changes depending on whether the second friction engaging device is engaged or disengaged, which makes transitional control of the engaging torque when engaging and disengaging the first friction engaging device difficult, for example.